Inertial sensor

Abstract

A movable part rotates about a rotation axis, which passes through a support, when an inertial force in a detecting direction is applied to an inertial sensor. The movable part includes a first region and a second region displaced in a direction opposite to a direction of the first region when the inertial force is applied. A second substrate includes first and second detection electrodes opposed to the first and second regions, respectively. The first detection electrode and the second detection electrode are provided symmetrically with respect to the rotation axis. A cavity is provided symmetrically with respect to the rotation axis. In a direction perpendicular to the detecting direction and a direction in which the rotation axis extends, a length from the rotation axis to an end of the first region and a length from the rotation axis to an end of the second region are different.

What is claimed is: 
     
       1. An inertial sensor comprising:
 a movable part disposed in a cavity surrounded by a first substrate, 
 a second substrate provided above the first substrate, 
 a plurality of sidewalls including a first side wall, a second side wall, and other side walls, and 
 a support provided in contact with the first substrate and the second substrate to support the movable part, wherein
 the movable part is a movable part configured to rotate about a shaft which is connected to the support, when an inertial force in a detecting direction is applied to the inertial sensor, the shaft having a longitudinal axis; 
 the movable part including a first region and a second region displaced in a direction opposite to a direction of the first region when the inertial force is applied, 
 the second substrate includes a first detection electrode opposed to the first region and a second detection electrode opposed to the second region, 
 the first detection electrode and the second detection electrode are provided symmetrically with respect to the longitudinal axis of the shaft, 
 the first and second regions each have a distal end that is farthest from the longitudinal axis of the shaft, 
 a distance from the longitudinal axis of the shaft to the distal end of the first region is different from a distance from the longitudinal axis of the shaft to the distal end of the second region, 
 a distance from the longitudinal axis of the shaft to the first side wall, which is adjacent to the distal end of the first region, is the same as a distance from the longitudinal axis of the shaft to the second side wall, which is adjacent to the distal end of the second region, 
 the longitudinal axis of the shaft extends through the other side walls rather than through the first and second side walls, and 
 the cavity is X-axis symmetrical with respect to the support, so that the cavity is symmetrical with respect to a rotation axis that passes the support, such that a dimension of the cavity, along the X-axis, on either side of the support, is the same. 
 
 
     
     
       2. The inertial sensor according to  claim 1 , wherein
 the length from the longitudinal axis of the shaft to the end of the second region is larger than the length from the longitudinal axis of the shaft to the end of the first region, and 
 the second substrate includes a diagnosis electrode that is opposed to the second region. 
 
     
     
       3. The inertial sensor according to  claim 1 , further comprising a mold resin package set in contact with the second substrate. 
     
     
       4. The inertial sensor according to  claim 1 , wherein the first substrate, the second substrate, and the movable part are formed of silicon. 
     
     
       5. The inertial sensor according to  claim 1 , wherein the inertial force is acceleration in the detecting direction. 
     
     
       6. The inertial sensor according to  claim 1 , wherein longitudinal axes of the first side wall and of the second side wall extend along a direction that is more similar to a direction of the longitudinal axis of the shaft than to a direction of another axis that is perpendicular to the longitudinal axis of the shaft. 
     
     
       7. The inertial sensor according to  claim 6 , wherein the longitudinal axis of the shaft is parallel to: i) the longitudinal axis of the first side wall, and ii) the longitudinal axis of the second side wall.